Throughout the world, passenger cars and trucks wear out millions of tires every year. Unfortunately, it is difficult to dispose of the used tires. Burning is usually prohibited because of air pollution concerns, and burying can lead to landfill contamination. As a result, used tires tend to accumulate creating eyesores and environmental hazards.
A particularly desirable way to dispose of used tires is to recover hydrocarbons and carbonaceous materials from the tires. The hydrocarbons can be used as fuel sources replacing expensive petroleum products, and the solid carbonaceous products have many end uses.
The conversion of rubber into fuels is generally known. Roy (U.S. Pat. No. 4,740,270) relates to the vacuum pyrolysis of tires at a temperature of from about 360-415 degrees centigrade (hereinafter ".degree.C") under pressures of less than about 725 millimeters of mercury (hereinafter "mm Hg") absolute. Solbakken et al. (U.S. Pat. No. 4,284,616) relates to the pyrolysis of tire fragments at approximately 454.degree.-566.degree. C. for 30 to 10 minutes under an oxygen limited, hydrocarbons vapor atmosphere at about 310-1138 mm Hg absolute. Solbakken et al. (U.S. Pat. No. 4,250,158) relates to the pyrolysis of tire fragments at approximately 454.degree. C. for 5 to 10 minutes under an oxygen limited, hydrocarbon vapor atmosphere at about 310-621 mm Hg absolute. Chambers (U.S. Pat. No. 4,235,676) relates to the heating of shredded rubber tires at a temperature of 427.degree.-816.degree. C. in the absence of air and/or oxygen, at a pressure of from about 608-658 mm Hg absolute. Herbold et al. (U.S. Pat. No. 4,084,521) relates to the pyrolysis of waste products containing hydrocarbons by heating the material at a sub-atmospheric pressure and a preferable temperature of between 400.degree.-800.degree. C.
The processes and apparatus of the prior art have several disadvantages. They are generally not capable of producing liquid hydrocarbons having low sulfur content. As a result, the liquid hydrocarbons produced by such processes and apparatus create high sulfur emissions when burned. Alternatively, the liquid fuels must be further processed to remove sulfur before being used as fuels.
The existing processes and apparatus also involve significant fire and explosion risk due to the presence of oxygen during preheating or pyrolysis. Other drawbacks of the processes and apparatus of the prior art include the fact that they often produce high levels of emissions and produce secondary wastes. Some processes and apparatus also use dangerous catalysts.
A process and apparatus has now been developed that overcomes the above-noted problems and also has numerous other advantages that will be apparent to those skilled in the art.